WT1 gene (Wilms' tumor 1 gene) was identified as a gene responsible for Wilms tumor which is a renal cancer in children (Non-patent Documents 1 and 2). WT1 is a transcription factor having a zinc finger structure. At the beginning, the WT1 gene was considered to be a tumor suppressor gene. However, subsequent studies (Non-patent Documents 3, 4, 5 and 6) showed that the WT1 gene rather functions as an oncogene in hematopoietic tumors and solid cancers.
The WT1 gene is expressed at high levels in many types of malignant tumors. Then, it has been examined whether or not the WT1 gene product free of mutations, which is an autologous protein, has immunogenicity in a living body. The results revealed that the protein derived from the WT1 gene which is expressed at high levels in tumor cells is fragmented through intracellular processing, the resulting peptides form complexes with MHC class I molecules, and the complexes are presented on the surfaces of cells, and that CTLs recognizing such complexes can be induced by peptide vaccination (Non-patent Documents 7, 8 and 9). It was also shown that in a mouse immunized with a WT1 peptide or a WT1 cDNA, transplanted tumor cells expressing a WT1 gene are rejected with a high probability (Non-patent Documents 7 and 10), while normal tissues expressing physiologically the WT1 gene are not damaged by the induced CTLs (Non-patent Document 7). It was shown in in vitro experiments using human cells that when Db126 peptide or WH187 peptide (amino acids 187-195 of SEQ ID No: 1, SLGEQQYSV) having a high ability to bind to an HLA-A*0201 molecule, which is one of human MHC class I molecules, is used to stimulate human peripheral blood mononuclear cells having HLA-A*0201, WT1-specific CTLs are induced, the induced CTLs have a cytotoxic activity specific for tumor cells expressing endogenously a WT1 gene at high levels, and the cytotoxic activity of such CTLs is HLA-A2-restricted (Non-patent Document 11). It was shown in in vitro experiments in human cells using WT1 peptide that matches HLA-A*2402 (which is found most frequently in Japanese people among HLA-A alleles) (WT1235; amino acids 235-243 of SEQ ID No: 1, CMTWNQMNL) that WT1-specific CTLs (TAK-1) are induced (Non-patent Document 12), and the induced CTLs do not suppress the colony-forming activity of normal hematopoietic stem cells which partially express physiologically a WT1 gene (Non-patent Documents 12 and 13). These reports strongly suggest that not only in mice but also in human beings, WT1-specific CTLs can be induced, such CTLs have a cytotoxic activity against tumor cells expressing a WT1 gene at high levels, but do not have a cytotoxic activity against normal cells expressing physiologically a WT1 gene (Non-patent Documents 7, 10, 11, 12 and 13).
The WT1 gene product is present as a nuclear protein, and is processed by proteasomes in cytoplasm to be fragmented into peptides. The fragmented peptides are transported into endoplasmic reticulum lumen by TAP (transporter associated with antigen processing) molecules, form complexes with MHC class I molecules, and are presented on the surfaces of cells. WT1-specific CTLs are induced as a result of recognition of WT1 peptide-MHC class I molecule complexes by CTL precursor cells via TCR, thereby exerting a cytotoxic effect on tumor cells presenting a WT1 gene product through MHC class I molecules (Non-patent Documents 7, 8 and 9). Then, it is required at least that a WT1 peptide used in cancer immunotherapy targeting a WT1 gene product is in the form that binds to an MHC class I molecule in a living body. However, MHC class I molecules are diverse and amino acid sequences of the WT1 peptides binding to respective MHC class I molecules are different from each other. Therefore, it is required to provide a peptide matching each subtype of MHC class I. However, only HLA-A*2402 molecule-, HLA-A*0201 molecule-, HLA-A*2601 molecule- and HLA-A*3303 molecule-restricted peptides are known as HLA molecule-restricted WT1 peptides to date (Patent Document 1, Non-patent Document 11, Patent Document 2 and Patent Document 3, respectively). Thus, there is a need to find an HLA-A*1101-restricted WT1 peptide.
Patent Document 1: WO 2003/106682
Patent Document 2: WO 2005/095598
Patent Document 3: Japanese Patent Application No. 2006-45287
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